Ghost Forests of the Pacific Northwest (evidence for Giant earthquake & tsunami)

Novice

What is the evidence for a Giant earthquake and Tsunami?

Ghost forests are part of the evidence that a Great earthquake and devastating tsunami occurred last on January 26th, 1700 in the Pacific Northwest. 
This simplified animation illustrates both the subduction-zone processes that lead to a "ghost forest" as well as the evidence that scientists collected to determine that the Pacific Northwest has had many great earthquakes and tsunamis in the past, and will again in the future.

This is based on the work of Brian Atwater who published his findings in the the book "The Orphan Tsunami of 1700" (USGS Professional Paper 1707) available online.

Tree drowning sequence of graphics is from the book, "At Risk: Earthquakes and Tsunamis on the West Coast ", by John Clague, Chris Yorath, and Richard Franklin, Tricouni Press, 2006

Keypoints:

Evidence:

  • Tectonic relationships indicate a Great earthquake is possible
  • Dead trees provoked geologists to study sand and mud deposits along the coast
  • Native American stories told of a great earthquake and tsunami seven generations back
  • Carbon dating of the dead trees indicated that they were drowned  between 1695 and 1710
  • Subsequent tree-ring analysis indicated the trees died between late 1699 and early 1700
  • Japanese written records tell of a tsunami that arrived withouth the warning of ground shaking.